The present disclosure relates to non-contact charging devices for charging secondary batteries mounted, for example, on electric propulsion vehicles (electric vehicles and hybrid electric vehicles) in a non-contact fashion.
Technologies using a magnetic field, an electric field, a radio wave, etc., have been developed to achieve power transfer in a non-contact fashion. The non-contact power transfer technology does not require any wires for connecting a power feeding device and a power receiving device, and users do not have to connect the devices, and do not have to worry about leakage and an electric shock in the event of rain.
In the non-contact power transfer, for example, positional relationship between the power feeding device and the power receiving device is important for enhanced efficiency. In this regard, a technology of providing a resonance part for resonating an AC signal in each of the power feeding device and the power receiving device has been proposed to reduce a constraint of the positional relationship between the power feeding device and the power receiving device (see, e.g., Japanese Unexamined Patent Publication No. 2009-296857).
According to the technology taught by Japanese Unexamined Patent Publication No. 2009-296857, a harmonic content having the same frequency as a frequency of a commercial power supply is superimposed on power output from the power feeding device. As a result, a current or voltage ripple of the harmonic content occurs in the output of the power feeding device, and a ripple occurs also in an output of the power receiving device, i.e., an output current to a battery, etc.
A system of connecting a power supply and an electric propulsion vehicle via wires has been used to charge the electric propulsion vehicle, etc. In the wired system, high-speed feedback control is available when the ripple is detected in the current output to the battery. In the non-contact charging system, however, the high-speed feedback control cannot easily be performed because the power receiving device is wirelessly notified that the ripple is detected in the output current.
As a solution to the above problem, a technology has been proposed that three column circuits (converters) each comprising a serially-connected four stage circuit are connected in parallel to share a plurality of smoothing capacitors, and each of the column circuits is driven by shifting their phases by 2π/3 (rad) (see, e.g., Japanese Unexamined Patent Publication No. 2008-263715). In this technology, the voltage ripple can be reduced by sharing a charge/discharge current to the plurality of smoothing capacitors among the column circuits.